Small Replicated Topology

By replicating directory data across servers, you can reduce the access load on
a single machine, improving server response time and providing horizontal read scalability. In
addition, replication can be used to ensure availability of data in the event
of machine failure.

Note that you cannot use replication to scale write operations because a write
operation to one directory server results in a write operation to every other
server in the topology. The only way to scale write operations horizontally is
to split the directory data among multiple databases and place those databases on
different servers.

The centralized replication model in Sun OpenDS Standard Edition separates user data from
replication metadata. In this model, the server that stores the user data is
called the directory server. The server that stores the replication metadata is called
the replication server. This approach simplifies the management of replication topologies and can
improve performance.

For small deployments, you can set up replication by putting the replication servers
and directory servers on the same system. You can further simplify administration by
running the replication server and the directory server on each system in a
single process.

The following diagram shows how replication is used to ensure availability and to
provide read scalability in a small topology.